A push-to-talk device is a device capable of participating in a Direct Connect™ or Walkie-Talkie phone call. The device works by having a user push a button to transmit and release the button to receive signal transmitted by other user(s).
In a device with two processors, one processor is used as a radio chip and has an RF interface and a radio push-to-talk key for originating or participating in a Direct Connect™ or Walkie-Talkie phone call.
The second processor is a control chip. This chip has access to the button used for the push-to-talk capability that is the user interface for the device.
The radio chip and the controller chip are linked to communicate using a protocol command/response. Every push-to-talk button press or release on the controller chip must be relayed to the radio chip using a protocol command and the controller chip must wait for a response from the radio chip. This leads to synchronization problems due to protocol round trip delays, changes in the user's choice while waiting for a response, or the radio chip rejecting the command from the controller chip for various reasons. These problems are common in dual processor equipped devices with push-to-talk capabilities.